Container with improved lid seal

ABSTRACT

A container adapted to be sealed with a lid is disclosed. The container cup has a lip with a raised sealing bead along its length. During sealing, the raised sealing bead compresses, thereby stretching the adhesive layer on the lower portion of the lid out of the way and forming a direct welded seal with the heat-resistant layer of the lid. The adhesive to either side of the sealing bead forms an adhesive seal between the lid and the remaining portion of the lip. This type of double seal is particularly effective in forming a durable, consistent seal when product is present on the lip of the container. The welded seal is also well suited to situations when the cup may be warped or the sealing bead is otherwise caused to be higher along some portion of its length than along other portions.

FIELD OF THE INVENTION

[0001] The invention relates broadly to containers, and in particularrelates to a container having a peel-away lid with a dual seal.

BACKGROUND OF THE INVENTION

[0002] Many types of food products, both liquid and solid, are packagedin containers with peel-off lids. Such containers are often designed tohold single portions of items such as condiments and toppings, and arethus referred to as “portion cups.” Portion cups are commonly found inrestaurants and contain such products as margarine, sour cream, andsalad dressings. Solid materials that may be packaged in portion cupsinclude ground pepper and various other seasonings. Portion cups areavailable in various sizes matched to the normal portion of thematerials they are designed to contain. The container itself isgenerally formed of a plastic material, and may be molded in manyshapes, including cylindrical, rectangular, and frustoconical varieties.

[0003] Portion cups have become popular because they may be producedrelatively inexpensively while offering great convenience to theconsumer. Such containers may be easily opened without the need fortools or opening devices. Generally, such containers are formed with alip or flange extending laterally outward from the open top, to whichthe lid is sealed with some type of adhesive. The lid generally includesa tab or other handhold portion that extends beyond or above the lip. Bygripping the tab and pulling back across the top of the lid, theconsumer may easily open the container without spilling its contents.

[0004] One of the chief difficulties encountered in designing containerswith peel-off lids is the maintenance of a consistent seal strength forall such containers produced. Numerous factors may affect the sealstrength for the lids of such containers, such as the temperature atwhich the seal is made, the pressure applied to the lid during thesealing process, and the particular properties of the adhesive used.When a seal is formed that is too strong, the container becomesdifficult to open, and may lead to the consumer using a knife or otherpotentially dangerous methods of reaching the contents inside. If theseal strength is too weak, then the container may leak during shipmentor storage. Rough handling during shipment is a common problem forcontainers of this sort, as they are most often dropped into large boxesin groups of several hundred with no special padding or packaging toprotect them from contact with other containers. If a container spillsduring shipment under these conditions, the entire box of product may beruined as the contents of one or a few containers spills onto the othercontainers. Various environmental factors such as temperature andhumidity may weaken seal strength during storage even when the sealstrength was within specified tolerances at the time of manufacture.Consumers will reject a container that is not properly sealed, and thedefect may reflect poorly on the food vendor that offered the product tothe consumer.

[0005] Still another problem encountered in sealing containers withpeel-away lids is that some portion of the packaged product may bepresent on the lip of the container prior to seating of the lid duringthe sealing process. Liquids may splash or spill onto the lip of suchcontainers during filling, and powders or granulated materials maysettle onto the lip of such containers in the form of a dust. Thisproblem is exacerbated by the high speed at which the filling operationmust proceed in order to keep production costs low. When a lid isapplied to a container when such material is present on the container'slip, the seal in that region of the lip will be poor and the containeris far more likely to leak during shipment or storage.

[0006] The prior art includes various attempts to improve the durabilityand consistency of the lid seal for peel-off lid containers. Forexample, U.S. Pat. No. 5,316,603 to Akazawa et al. teaches a containerhaving “microdents” along a sealing layer in the flange or lip portionof the container, or along the sealing portion of the lid. Thesemicrodents are arranged in various patterns in the form of dots alongthe sealing surface between the lip and lid of the container.

[0007] U.S. Pat. No. 5,979,748 to Drummond et al. teaches a tubularcontainer with a lid having an adhesive layer; the lid is sealed usingheat and pressure. As the lid is pressed onto the lip of the container,the adhesive in the adhesive layer is pressed outward from the center ofthe lip, forming an outer adhesive bead and inner adhesive bead from theadhesive build-up at the edges of the lip. A thin layer of adhesive mayremain between the lid and container lip, or the container and lid maymake contact in the center of the lip, such that the entire seal isformed by the inner and outer adhesive beads.

[0008] U.S. Pat. No. 4,379,008 to Gross et al. teaches a method forattaching together two pieces of cardboard using a heater with truncatedpyramid-shaped projections. One piece of the cardboard has an adhesivelayer that contacts the other piece. As the heater is pressed onto theupper piece of cardboard, pressure from the projections causes adhesiveto flow outward from beneath the projections and collect in areasbetween the projections.

[0009] U.S. Pat. No. 4,659,405 to Walter teaches a lid and containerseal wherein an incompressible rib is formed along the lip of thecontainer. The lid has an adhesive layer that forms a seal with the rib,but the adhesive does not necessarily contact the flat portion of thelip, and no seal with the flat portion of the lip is formed. The rib issealed to the lid with adhesive, and does not deform during sealing. Thepressure applied in this sealing process is not great enough such thatthe rib pushes through the adhesive layer and comes into contact withthe portion of the lid beneath the adhesive layer.

[0010] U.S. Pat. No. 4,961,513 to Gossedge et al. teaches a containerwith a lip having a plastic upper surface and a lid with a plastic lowersurface. The lid and container lip are heat sealed together, forming two“ears” of material at the outer and inner edges of the seal. The “ears”consist of a plastic core formed of material from the lip which isjoined to the lip by a thin “root,” and an envelope encasing the coreformed of material from the lid.

[0011] None of the prior art methods described above adequately overcomethe problems of forming a consistent seal on a container, particularlywhen the container may contain overflow of product on the container lip.This problem, particularly acute when solid materials are to be placedin the container, will interfere with each of these sealing methods,resulting in a weak seal when material is present. What is desired is amethod for sealing a peel-off lid on a container such that a tight sealis formed even when material may be present on the lip of the containerduring the sealing process.

SUMMARY OF THE INVENTION

[0012] The present invention overcomes the limitations of the prior artthrough a double sealing method to provide a consistent seal even whenthe lip of the container may be contaminated with overflow product. Thecontainer comprises a lid and a cup, with the cup having a lip with araised sealing bead that runs along its length. The lid includes anadhesive layer on its lower side. The raised sealing bead iscompressible, which allows a weld to form between the bead and the lidwhen the lid is pressed into place, while at the same time an adhesiveseal is formed between the lid and the remaining portion of the lip.Thus the lid is sealed to the container both by the weld between thesealing bead and the lid, and by the adhesive bond between the lid andthe remaining portion of the lip.

[0013] To attach the lid to the container according to the presentinvention, the lid is positioned over the cup and pressed into placewhile heat is applied. The heat causes the adhesive to bond the lip tothe lid. The raised bead, however, will compress and deform underpressure, thereby stretching adhesive on the lid directly above the beadto either side of the bead, thus allowing the bead and lid to makedirect contact. This direct contact is necessary for the weld to form.In addition, the smaller surface area of the bead with respect to thelid as a whole results in much greater pressure along the bead duringsealing than would be experienced on the lip if no bead were used.Direct contact between the bead and lid under this high pressure causesthe weld between the bead and lid, thereby forming an additional sealbetween the container and lid.

[0014] Any irregularities in the height or shape of the bead will besmoothed during the sealing process as a result of the bead'scompressibility. If the lip of the container should become deformed suchthat the bead has a high point, that portion of the bead will be subjectto correspondingly greater pressure during the sealing process. Thishigher pressure will cause the bead to compress further at the highpoint, thereby evening the height of the bead along its lengthautomatically as sealing takes place. In a preferred embodiment, thebead has a relief pocket beneath it that increases the compressibilityof the bead during the sealing process, enhancing the ability of thebead to stretch adhesive away from the lid to allow the weld to form,and increasing the capacity of the bead to even itself in height as aresult of pressure during sealing.

[0015] This double sealing method is particularly well-suited to forminga seal when material has flowed onto the lip of the container. Thedirect weld between the bead and the lid is along a relatively smallsurface area of the lip, which reduces the likelihood that any materialfalling onto the lip would interfere with this bond. More importantly,however, the relatively high pressure between the bead and the lidduring sealing will tend to force any material present on the bead toeither side of the bead, thereby allowing a firm, solid seal to takeplace. This is particularly effective with respect to liquid or flowablematerials that may have spilled onto the lid, since they may be pushedaside from the bead during sealing. Powders and granulated solids arealso pushed aside by the process, thereby allowing a solid welded sealto form.

[0016] It is therefore an object of the invention to provide a containerwith a peel-off lid that has a reduced likelihood of leaking or spillingduring shipment or storage.

[0017] It is a further object of the invention to provide a containerwith a peel-off lid that has a double seal between the lid and containerlip.

[0018] It is a further object of the invention to provide a containerthat will seal when product is spilled onto the lip of the containerprior to sealing.

[0019] It is a further object of the invention to provide a containerwith a sealing bead along its lip that will properly seal when thesealing bead has been warped or deformed prior to sealing.

[0020] Other objects of the invention will be evident from thedescription of the preferred embodiments of the invention and thedrawings that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a perspective view of a container according to apreferred embodiment of the present invention, with the lid shownpartially peeled away.

[0022]FIG. 2 is a cut-away view of the lip of a container according to apreferred embodiment of the present invention.

[0023]FIG. 3 is a cut-away view of the lip of a container according to apreferred embodiment of the present invention, showing a portion of thelid of the container positioned in place prior to sealing.

[0024]FIG. 4 is a cut-away view of the lip of a container according to apreferred embodiment of the present invention, showing a portion of thelid of the container after sealing.

[0025]FIG. 5 is a cut-away view of the lip of a container according to apreferred embodiment of the present invention, showing a portion of thelid of the container positioned in place prior to sealing when particlesof product are present on the container lip.

[0026]FIG. 6 is a cut-away view of the lip of a container according to apreferred embodiment of the present invention, showing a portion of thelid of the container after sealing when particles of product are presenton the container lip prior to sealing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Referring now to FIGS. 1 and 2, a preferred embodiment of acontainer according to the present invention can be described. Container10 is a portion cup constructed of cup 11 and lid 12. Container 10 ispreferably formed of a plastic material, preferably high densitypolyethylene or polypropylene, but can be of any material of sufficientstrength to protect the product within the cup. Cup 11 has an open topand is generally frustoconical in shape, but can be of any desired shapeas appropriate for the product to be packaged and for the means ofshipping and storing container 10, including cylindrical and rectangularshapes. In one preferred embodiment, using a cup 11 of invertedfrustoconical shape designed to hold 1.25 fl. oz. of product, cup 11 haswalls formed of high density polyethylene having a thickness of 0.017inches, with a height of 1.135 inches and a 10° slope on its sides fromthe vertical. Also in a preferred embodiment, cup 11 has a cylindricalportion 15 that connects its frustoconical portion 17 to lip 14,cylindrical portion 15 having a height of 0.164 inches and an insidediameter of 2.169 inches.

[0028] Cup 11 has a lip 14 that extends transversely from the open topof cup 11 to which the periphery of lid 12 is sealed. Lip 14 must be ofsufficient width to form a seal with lid 12 as described below. In apreferred embodiment of cup 11 designed to hold 1.25 oz. of product, lip14 is annular and has a width of 0.115 inches.

[0029] Lid 12 is generally designed to match the size and shape of lip14 for a smooth fit, but also includes a tab 13 that extends beyond lip14 such that the user may grip tab 13 easily to open container 10. Asshown in FIG. 1, container 10 has been partially opened by pulling tab13 back across the open top of cup 11. Referring now to FIG. 3, thethree layers of lid 12 are shown; the lower layer is adhesive layer 20,which is topped by a middle foil layer 22, followed by an outer paperlayer 24. Paper layer 24 may preferably be constructed of C1S StainlessPaper, which is generally regarded as a “grease-proof” material. Outerpaper layer 24 is preferably attached to middle foil layer 22 using LDPEor EEA adhesive as are known in the art. Middle foil layer 22 ispreferably formed of a thickness in the range of 0.0005 to 0.001 inches,and may be formed of any alloy that provides a sufficient moisturebarrier between outer paper layer 24 and the product within container10. Adhesive layer 20 may preferably be formed in a film, which isattached to middle foil layer 22 with an LDPE adhesive or urethaneadhesive. In the preferred embodiment, adhesive layer 20 is about0.00125 inches thick.

[0030] Again referring to FIG. 1 and FIG. 2, raised sealing bead 16 runsthe length of lip 14. In the preferred embodiment, sealing bead 16 hasrelief pocket 18 underneath it and running along its length. In thisconfiguration, the wall thickness of lip 14 remains relatively constantinstead of becoming thicker at sealing bead 16. In the preferredembodiment of container 10 designed to hold 1.25 oz. of product, sealingbead 16 may have a width of 0.050 inches and a height above lip 14 of0.010 inches, and relief pocket 18 has a width of 0.014 inches and depthof 0.011 inches. Also in a preferred embodiment, sealing bead 16 islocated approximately mid-way between the inner and outer edges of lip14.

[0031] Referring now to FIGS. 3 and 4, the process for sealing lid 12onto cup 11 according to a preferred embodiment of the invention isshown. Lid 12 is fed into place above cup 11 and aligned properly sothat the outer edge of lid 12 will match the outer edge of lip 14 whensealing is complete. It should be noted that, as shown in FIG. 3, lid 12must extend slightly from the edge of lip 14 prior to sealing because ofthe compression of sealing bead 16 as described below. The amount ofoffset in lid 12 and lip 14 necessary such that they will be properlypositioned relative to one another after the seal is formed depends uponthe width and height of sealing bead 16, as well as the thickness of thematerial used to form lip 14.

[0032] Once lid 12 is in place above lip 14, heater head 19 descendsupon lid 12 as shown in FIG. 3. Heater head 19 applies both heat andpressure to lid 12 as well as to lip 14. In the preferred embodiment,heater head 19 is at a temperature of about 400 degrees Fahrenheitduring sealing, and heater head 19 applies approximately 40 pounds persquare inch of pressure to lid 12 for a duration of 0.5 seconds. Heatreaches lip 14 conductively through lid 12 from heater head 19. As shownin FIG. 3, when heater head 19 just touches lid 12, adhesive layer 20 oflid 12 is in contact with sealing bead 16 but is not in contact with theother portions of lip 14. Foil layer 22 is not in contact with eithersealing bead 16 or lip 14.

[0033] As heater head 19 presses down upon lid 12, a large amount ofpressure is placed upon sealing bead 16. This pressure is considerablygreater than the pressure that would be effected upon lip 14 if sealingbead 16 were not present, because of the correspondingly lesser areaoccupied by the face of sealing bead 16 as compared to lip 14. Thispressure causes sealing bead 16 to compress as shown in FIG. 4, therebyreducing the height of sealing bead 16 and increasing both the width ofsealing bead 16 and lip 14. This pressure and deformation of sealingbead 16 also causes that portion of adhesive layer 20 directly abovesealing bead 16 to “stretch” to the inside and outside of sealing bead16. It should be noted that the heat from heater head 19 serves toactivate adhesive layer 20, which partially liquefies adhesive layer 20thereby furthering the “stretching” process.

[0034] Once the portion of adhesive layer 20 above sealing bead 16 isremoved in this manner, sealing bead 16 and foil layer 22 of lid 12 comeinto direct contact. This direct contact further heats sealing bead 16,partially melting a portion of the top of sealing bead 16 and therebywelding it to lid 12 at foil layer 22. It should be noted that reliefpocket 18 makes sealing bead 16 compressible at much lower pressuresfrom heater head 19.

[0035] As shown in FIG. 4, the pressure of heater head 19 onto lid 12also causes adhesive layer 20 of lid 12 to come into contact with lip14. This forms an adhesive bond between lid 12 and lip 14 to the insideand outside of sealing bead 16. The result of this process is a doubleseal between cup 11 and lid 12; a welded seal between sealing bead 16and foil layer 22, and an adhesive seal between lip 14 and adhesivelayer 20.

[0036] Referring now to FIGS. 5 and 6, the sealing method describedabove is applied to the situation where particles of product 26 from cup11 are present on lip 14. The high pressure present on top of sealingbead 16 as explained above, in addition to the compression of sealingbead 16 which creates a “stretching” effect on adhesive layer 20,combine to force particles 26 away from sealing bead 16 and toward oneedge of lip 14. In the example of FIG. 6, one of particles 26 remainstrapped between adhesive layer 20 and lip 14, thereby interfering withthe adhesive seal between lid 12 and lip 14. If sealing bead 16 were notpresent, the resulting seal might be insufficient to contain the productwithin container 10 during shipment and storage. But because sealingbead 16 has formed a weld with foil layer 22 of lid 12, container 10 ismore likely to remain uncompromised even during rough handling or longstorage after shipment. It should be noted that in the case of aparticle 26 that is present on lip 14 near its inner or outer edge, the“stretching” effect on adhesive layer 20 is likely to push that particle26 completely off of lip 14, thereby allowing a firm adhesive seal totake place between lid 12 and cup 11 in addition to the welded sealresulting from the use of sealing bead 16.

[0037] Referring again to FIGS. 4, it will now be described how thepresent invention allows for automatic compensation when sealing bead 16may be of uneven height. This may occur for a number of reasons,including warping of cup 11 due to temperature, rough handling of cup 11prior to or during filling, or imprecise seating of cup 11 during thefilling process. If certain points on sealing bead 16 are higher thanothers, then these points will first make contact with heater head 19 asit descends during the sealing process. Because only one point or a fewpoints will be in contact with heater head 19, the pressure at thesepoints will be very high, corresponding to the very small area overwhich the force of heater head 19 is spread. This very high pressurewill serve to compress these points on sealing bead 16 to a greaterextent than the lower portions, thereby resulting in a sealing bead 16that is compressed to a roughly equal height at all points along itslength at the completion of the sealing process. Because sealing bead 16will be compressed to a relatively equal height at all points along itslength, the resulting weld between sealing bead 16 and foil layer 22 oflid 12 will be of equal strength at all points along sealing bead 16,thereby maximizing the ability of container 10 to withstand roughhandling or other environmental factors that might cause container 10 tootherwise leak or spill.

I claim:
 1. A container, comprising: (a) a cup with an open top; (b) asubstantially flat lip circumscribing the open top of said cup; and (c)an elongated sealing bead on the surface of said lip, wherein saidsealing bead comprises a substantially flat upper surface.
 2. Thecontainer of claim 1, further comprising an elongated relief pocketbeneath said sealing bead.
 3. The container of claim 2, furthercomprising a lid that is sealed to said cup both at said lip and at saidflat upper surface of said sealing bead.
 4. The container of claim 3,wherein said lid comprises a lower adhesive layer and an upperheat-resistant layer.
 5. The container of claim 4, wherein saidheat-resistant layer of said lid comprises a middle foil layer and anupper paper layer.
 6. The container of claim 3, wherein the width ofsaid sealing bead is between one-third and one-half of the width of saidlip.
 7. The container of claim 3, wherein the width of said sealing beadis about fifty thousandths of an inch.
 8. The container of claim 7,wherein the width of said relief pocket is about fourteen thousandths ofan inch.
 9. The container of claim 3, wherein the shape of saidcontainer is at least partially one of cylindrical and frustoconical.10. The container of claim 9, wherein said lip, said bead, and saidrelief pocket are annular.
 11. A container adapted to receive a lid,comprising: (a) a cup with an open top; (b) a lip circumscribing theopen top of said cup; and (c) an elongated sealing bead on the surfaceof said lip, wherein said sealing bead is compressed with respect tosaid lip subsequent to the application of the lid onto said cup.
 12. Thecontainer of claim 11, further comprising an elongated relief pocketbeneath said sealing bead.
 13. The container of claim 12, furthercomprising a lid that is sealed to said cup both at said lip and at saidsealing bead.
 14. The container of claim 13, wherein said lid comprisesa lower adhesive layer and an upper heat-resistant layer.
 15. Thecontainer of claim 14, wherein said heat-resistant layer of said lidcomprises a middle foil layer and an upper paper layer.
 16. Thecontainer of claim 13, wherein the width of said sealing bead is betweenone-third and one-half of the width of said lip.
 17. The container ofclaim 13, wherein the width of said sealing bead is about fiftythousandths of an inch.
 18. The container of claim 17, wherein the widthof said relief pocket is about fourteen thousandths of an inch.
 19. Thecontainer of claim 13, wherein the shape of said container is at leastpartially one of cylindrical and frustoconical.
 20. The container ofclaim 19, wherein said lip, said bead, and said relief pocket areannular.